The Hooked Shortspear can be found in Out of the Abyss, page 224.
You gain a +3 bonus to attack rolls and damage rolls made with this magic weapon. When you hit a Fiend or an Undead with it, that creature takes an extra 2d10 Radiant damage.
While you hold the drawn weapon, it creates a 10-foot Emanation [Area of Effect] originating from you. You and all creatures Friendly [Attitude] to you in the Emanation [Area of Effect] have Advantage on saving throws against spells and other magical effects. If you have 17 or more levels in the Paladin class, the size of the Emanation [Area of Effect] increases to 30 feet.
On a hit with this weapon, the wielder can forgo dealing damage and attempt to trip the target, in which case the target must succeed on a Strength saving throw or fall prone. The DC is 8 + the wielder's Strength modifier + the wielder's proficiency bonus.
A light weapon is small and easy to handle, making it ideal for use when fighting with two weapons.